Palm trees are coming to Fifth Avenue this weekend. Tropically decorated Tommy Bahama Manhattan Island is the first restaurant in decades to open on the shopping corridor north of 42nd Street — with 150 seats in 6,700 square feet on the second floor, plus 50 more seats in the sidewalk-level Marlin Bar.

Both eatery and saloon are part of the mammoth deal Tommy Bahama made over two years ago at 551 Fifth Ave., the Fred D. French Building, at 44th Street. The 12-year lease for a combined 12,600 square feet includes the “island-inspired” sportswear/lifestyle brand’s new store, which opened two weeks ago.

How well “world-famous” (the quotation marks are theirs) coconut shrimp and macadamia nut-encrusted snapper does with locals remains to be seen. I’ve lunched at Tommy Bahama in Palm Desert, Calif., and have been pleasantly surprised.

But the restaurant launch is a bold stroke: Except for fast-food outlets and touristy TGI Friday’s at 604 Fifth, the avenue has not had a place to eat with a sidewalk entrance in several generations.

Tommy Bahama epitomizes the “new” Fifth Avenue between 42nd and 49th streets, which was long home mostly to second-class retailers and tourist-trap discount electronics and “art” galleries.

Of course, it’s improved enormously in recent years. Today there are Sweden’s H&M (including at its planned new location at 48th Street), Spain’s Zara, Britain’s Ted Baker and Canada’s Joe Fresh and Artizia. US brands include Urban Outfitters, Barnes & Noble, Build-a-Bear and Guess.

But the perception that the stretch is hot after generations of irrelevancy doesn’t mean it’s ready to rival the fabled blocks to the north. “Going out of business” outlets and under-utilized storefronts remain. How well their landlords exploit the new climate will determine whether the corridor retains its mixed-bag character or achieves an entirely fresh identity.

As Cushman & Wakefield retail powerhouse Brad Mendelson notes, much of the future lies in the hands of three major private landlords: Joseph Sitt, Joseph Moinian and Stanley Chera, who control crucial blockfronts and corners.

A major battlefront lies between 44th and 45th streets, where the entire west blockfront is controlled by a partnership including retail-savvy Chera’s Crown Acquisition and the east side by Moinian, who owns 535-545 Fifth Ave.

At host Jonathan Mechanic’s packed-as-always Fried Frank holiday party at Cipriani 42nd Street last week, Moinian enthused to us about his plan to convert the existing storefronts into a gleaming 100,000-square-foot glass-wrapped retail box.

He even sent us a rendering, but then decided not to discuss the details.

Across the street, Chera and partners reportedly hope to charge $1,500 a square foot for 50,000 square feet of store space, much of which became available when Syms and Filene’s Basement collapsed after they signed a lease two years ago.

Meanwhile, Sitt is tearing down 520 Fifth Ave. to put up a sleek new seven-story glass-wrapped space of 77,000 square feet.

It’s the first phase of a project that might eventually include an office tower.

The leasing agent, Sam Polese, couldn’t be reached.

At a different address owned by Sitt, 590 Fifth Ave. between 47th and 48th streets, his rep said the ask is $1,250 per square foot for a vacant space.